As I understand it, using various options for the S column in siunitx, I may produce columns containing both numerical and nonnumerical entries. I may have the numerical entries aligned at their decimal points. I may have the text entries either left-, right-, or center- justified with respect to the column's width.

Is it possible to have the numerical entries aligned by their decimal, while controlling the text entries' alignment as it relates to the decimal marker?

To complicate things further, is it possible to apply alignments differently row by row? In particular, could I leave column-centered alignment for the head entry of a column, while making my special decimal marker-based alignment apply to later entries?

The following MWE sort of produces what I want with exaggerated numbers, but I have manually forced some space in the last two entries to make it happen. I want to not have to do this.

Note that I do want a centered title, and that ideally I actually want the remaining text entries centered with respect to a point that is roughly 0.5\ex to the left of the decimal marker. Also, note that since I have such asymmetry between integer an fractional parts, I do not think that table-number-alignment=center-decimal-marker is helpful.

Can you elaborate on what you meant with “apply alignments differently row by row”. Isn't that what you get with your \heading macro?
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QrrbrbirlbelOct 27 '12 at 0:01

@Qrrbrbirlbel Thanks for your answer - I will try to apply it Monday when I again have access to my desktop. I believe that in my experiments, the text alignment from S was overriding the alignment c in my \heading macro. As I recall parameters like table-text-alignment=left made the c in my \heading command pointless. I may be misremembering though - I went through a lot of experimentation this morning.
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alex.jordanOct 27 '12 at 2:21

I just updated my answer so that is easier useable. If I understand it correctly, \multicolumn overrides SIunitx's stuff. And “Title” was actually typeset centered to the whole column …
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QrrbrbirlbelOct 27 '12 at 2:28

1

I'd also note that the business about wanting an alignment with offset is really outside of what siunitx was designed to handle. The intention of the S column is to align numerical columns, which it does a reasonable job of, but if you have very specific needs then there comes a point at which a custom solution is the best way forward.
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Joseph Wright♦Oct 27 '12 at 6:59

Output

Thanks for the answer. I can't play around with this until Monday, but at a glance I have a concern. I am working on a very long document with hundreds of tables like this. And I very much want a solution at the level of S. That is, I won't want to have to put anything more than a pair of braces around my non-numeric table entries, let siunitx and S detect what is numeric and what is not, and typeset accordingly. Can I modify S to wrap your tcenter around non-numeric entries?
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alex.jordanOct 27 '12 at 2:47

@alex.jordan: That might be a separate question, but you could possibly use the collcell package for that, although I don't think I have tried it with the S column.
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Peter GrillOct 27 '12 at 3:20